iMac starts with a white screen, and with fans at full throttle. What to do?

My friends aluminum iMac is acting very strange and refuses to start for seemingly no reason. After a power outage he attempted to turn it back on and now it starts up with the fans at full throttle and the screen is white. There is no startup noise and it just stays like this. Are there any steps I can take to troubleshoot the problem and maybe fix it. Any suggestions are greatly appreciated, thanks.

After an SMC reset the fans are no longer throttling up at start, but the white screen still stays there. I also tried a PRAM reset and the screen went black and just stayed black, so I don't think that worked. When attempting to boot up to the startup disk, the screen stayed white and the computer sounded like it was spinning up the disk and attempting to boot from it, but there was no boot noise or change in the screen. Also, i cannot eject the disk so there is now an install disk stuck inside the iMac. Is there anything else I could do to get the disk out and possibly make the computer startup?

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